Point mutations implicate repeated sequences as essential elements of the CYC7 negative upstream site in Saccharomyces cerevisiae

Tripartite structure of the Saccharomyces cerevisiae arginase (CAR1) gene inducer-responsive upstream activation sequence

Arginase (CAR1) gene expression in Saccharomyces cerevisiae is induced by arginine. The 5' regulatory region of CAR1 contains four separable regulatory elements--two inducer-independent upstream activation sequences (UASs) (UASC1 and UASC2), an inducer-dependent UAS (UASI), and an upstream repression sequence (URS1) which negatively regulates CAR1 and many other yeast genes. Here we demonstrate that three homologous DNA sequences originally reported to be present in the inducer-responsive UASI are in fact three exchangeable elements (UASI-A, UASI-B, and UASI-C). Although two of these elements, either the same or different ones, are required for transcriptional activation to occur, all three are required for maximal levels of induction. The elements operate in all orientations relative to one another and to the TATA sequence. All three UASI elements bind protein(s); protein binding does not require arginine or overproduction of any of the putative arginine pathway regulatory proteins. The UASI-protein complex was also observed even when extracts were derived from arg80/argRI or arg81/argRII deletion mutants. Similar sequences situated upstream of ARG5,6 and ARG3 and reported to negatively regulate their expression are able to functionally substitute for the CAR1 UASI elements and mediate reporter gene expression.

CYP1 (HAP1) regulator of oxygen-dependent gene expression in yeast. I. Overall organization of the protein sequence displays several novel structural domains

In the yeast Saccharomyces cerevisiae the CYP1 gene that modulates the expression of iso1-(CYC1) and iso2-cytochrome c (CYP3) structural genes gives rise to two classes of mutated alleles; one class, represented by CYP1-18, has opposite effects on CYC1 and CYP3, it reduces the expression of CYC1 while it stimulates that of CYP3. The other class, represented by cyp1-23 or the related allele hap1-1, reduces the expression of both CYC1 and CYP3 genes. Genetic data suggested that the CYP1 product is a positive regulator of the cytochrome c genes. The CYP1-18 allele has been cloned. We show here that the iso2 overproducer function of CYP1-18 is included in a 5300 base XhoI-PstI fragment. The sequence of this fragment reveals a unique, long, uninterrupted open reading frame of 4449 nucleotides able to encode a protein of 1483 amino acid residues. The predicted product of this open reading frame contains several interesting features. The N-terminal part of the protein resembles a nucleic acid-binding domain, in which two domains can be distinguished. The first is similar to a "finger" DNA binding motif, as found in TFIIIA and other regulatory proteins. The second consists of seven tandemly repeated sequences with a KCPVDH motif. Because of its structure, it is tempting to speculate that this region may act as a "redox sensor" folded around a metal atom or heme and involved in recognition of respiratory effectors. These two domains are separated by an "opa" sequence of 13 Gln residues. Implication of these domains for the function of CYP1-18 is discussed.